A Closer Look At Fixation For Fifth Metatarsal Fractures

Fifth metatarsal fractures are the most common of all metatarsal fractures.1 Avulsion fractures, Jones fractures and proximal diaphyseal fractures occur most frequently, but diaphyseal, neck and head fractures also occur.2 Clinicians can treat most of these fractures conservatively if the fractures are not significantly displaced.

The Jones fracture is well known for poor healing with immobilization, even if there is no displacement, making surgery an appropriate initial option. Diaphyseal fractures are almost always displaced, necessitating open reduction with internal fixation (ORIF). Avulsion fractures are the most common of all fifth metatarsal fractures. Authors have suggested that the mechanism of injury is the pull of the lateral band of the plantar aponeurosis in the supinated (inverted) foot. The peroneus brevis tendon has a broad lateral attachment at the base of the fifth metatarsal that may further contribute to displacement.3,4

The literature is filled with various types of fixation implants and techniques that advocate superior strength against axial load, pull out strength, bending and torque. Given the variety of fixation options, how does the surgeon select appropriate fixation? What is effective when you need to have a stable construct to prevent postoperative displacement, achieve optimal healing and resist the weightbearing forces of a non-adherent patient? What kind of fixation is best in patients with soft bone, those who smoke or for addressing other risk factors that surgeons typically encounter?

Salient Tips On Fifth Metatarsal Neck Fractures

Fifth metatarsal neck fractures are usually characterized by a transverse fracture resulting in lateral displacement of the head. The head may be displaced dorsally or plantarly, depending on the mechanism of injury. Although one could use a bone plate, the simple Kirschner wire (K-wire) is the fixation modality of choice. This is a fairly easy fracture to reduce by distraction. The surgeon can insert an 0.062 K-wire plantarly under the fifth toe through the base of the proximal phalanx and the fifth metatarsal head into the diaphysis. I would recommend inserting the K-wire as far proximally as possible even into the base.

When it comes to osteoporotic bone, one may use an additional K-wire for further stability to prevent rotation and add more stability against axial load. If the head is impacted into the diaphysis and one cannot distract it with closed methods, the surgeon can open the fracture site and use an elevator to separate the fracture. In this case, you can tilt the head dorsally so you can drive the K-wire through the fracture site of the head and out distally through the plantar aspect of the foot. Surgeons can use the wire as a joystick to aid in reduction and subsequently drive it proximally into the diaphysis.

How To Address Diaphyseal Fractures

Little has been written about diaphyseal fractures. These fractures begin at the lateral side of the neck or distal aspect of the shaft, and extend medially and proximally through the diaphysis. The fracture can be short and oblique, or extend into the proximal diaphysis and have a long spiral orientation. This fracture may be comminuted at the metatarsal neck and at the spike. This fracture is usually shortened, displaced medially and elevated. Given the displacement and diaphyseal location of this injury, one should reduce and fixate the fracture.

The most common fixation technique the lead author uses is a tubular plate with 2.7 mm cortical screws. Surgeons can accomplish reduction via distraction of the fifth toe to restore the length and applying a bone clamp to reduce the medial displacement in the diaphysis. One can use fluoroscopy to confirm reduction. The problem with the bone clamp is that it blocks lateral application of the plate so the lead author will insert a 0.062 K-wire through the fracture to maintain a reasonable degree of reduction and in a direction so it does not interfere with plate application.

One subsequently removes the clamp and applies the plate laterally, ensuring enough distal placement so the surgeon can insert at least one screw through the head depending on the characteristics of the fracture. The plate should also extend proximal enough so one can anchor at least two screws proximal to the fracture. You can usually accomplish this with a five- or six-hole plate. T-plates or L-plates also provide the ability to insert additional screws into the metatarsal head. Locking plates also enable the surgeon to insert two or even three screws distally, and locking plates are indicated in soft osteoporotic bone.

Many times, the fracture spike is so narrow that one cannot use an interfragmentary screw. Sometimes, the surgeon can use a smaller diameter 2.0 mm or 2.4 mm cortical screw to achieve interfragmentary compression but one should insert this screw prior to plate application. The tubular plate will function as a neutralization plate.

Essential Insights On Treating Jones Fractures

The Jones fracture occurs 1.5 to 3.0 cm distal to the tuberosity and at the articular surface of the fourth and fifth metatarsals.4 Given the poor healing or refracture that can occur with Jones fractures when clinicians opt for immobilization only, surgery is often an initial treatment, especially in active patients and athletes.

The Jones fracture lends itself to surgical repair because good exposure is easy to achieve and there is adequate bone both distal and proximal to the fracture to secure fixation modalities.

There are two likely options when surgery is the primary initial procedure. The first option is closed reduction with percutaneous fixation. We have found it easy to work with cannulated systems for these fractures. After reducing the fracture, insert a wire from the cannulated set through the base of the metatarsal across the fracture into the medullary canal. To avoid inadvertent perforation of the cortex, tap the wire and slowly advance it in the medullary canal with a small mallet. One can perform overdrilling as needed.

Proceed to make a small incision at the base of the metatarsal and insert the cancellous screw. The screw diameter is up to the surgeon. However, in a clinical and biomechanical study, Reese and colleagues determined that surgeons can achieve the best results when using the largest diameter screw that can fit in the medullary canal.5 This can be in the range of 4.0 mm to 6.5 mm, depending on the size of the bone.

Prior to surgery, one should measure the width of the medullary canal on the X-ray to determine the appropriate diameter screw. Also bear in mind that many fifth metatarsals have lateral diaphyseal bowing, which may not lend itself to using a long screw. In these cases, the tip of the screw may contact the distal medial surface of the metatarsal, resulting in displacement of the lateral portion of the fracture as one advances the screw. In the presence of lateral bowing, the lead author uses the shortest, widest screw possible for the Jones fracture.

A variation of the percutaneous intramedullary technique is to insert the screw from the base of the metatarsal into the medial cortex distal to the fracture. In a biomechanical study, Moshirfar and co-workers determined that bicortical cancellous screw fixation was much stronger than intramedullary cancellous screw fixation.6 This was supported by Husain and DeFronzo, who also compared the stability of bicortical and intramedullary screw fixation.7 They determined that the bicortical screw had superior load resistance over the intramedullary screw. The advantage of the percutaneous procedure is that one doesn’t have to perform dissection over the fracture site. This preserves both the periosteum and vasculature.

A second fixation option is to use a bone plate. The lead author will usually use a quarter tubular plate with 2.7 mm cortical bone screws. One can employ a one-third tubular plate with 3.5 mm cortical screws but occasionally, the prominent screw heads result in soft tissue irritation. Regardless of the type of plate one uses, the length is usually a four-hole to a six-hole.

The surgeon reduces the fracture and achieves interfragmentary compression by using a 2.7 mm screw from dorsal to plantar across the fracture. Then one would apply the bone plate. If you do not use the lag screw, you can apply the plate with eccentric drilling for compression. Surgeons can use locking plates for osteoporotic bone.

Key Considerations With Avulsion Fractures

Avulsion fractures comprise 45 to 93 percent of all fifth metatarsal fractures and there are several fixation techniques available.2,8-9 The unique consideration is that the fixation must counteract the pull of the peroneus brevis tendon. For larger fracture fragments, one can perform closed reduction with percutaneous intramedullary fixation and a cancellous screw. For smaller displaced fragments, comminuted bone, osteoporosis or patients who must bear weight because of comorbidities, tension band wire is a very effective modality. This is an effective fixation technique that Pauwels advocates.10

The technique involves exposing the fracture and achieving reduction. One would drive 0.062 Kirschner wires from the base across the fracture to just penetrating the medial cortex of the diaphysis. The surgeon would use two wires that are parallel to each other. After drilling a 2 mm hole distal to the fracture from dorsal to plantar, place a tension wire through the hole and loop over the two K-wires in a figure-of-eight fashion. One can tighten the wire dorsally and plantarly to achieve even compression across the fracture as needed.

Surgeons may also employ hook plates for the treatment of avulsion fractures. Surgeons originally used this technique for fixation of distal fibular fractures. Carpenter and Garrett recommend use of the hook plate on the fifth metatarsal base if the bone is comminuted.11 After exposing and reducing the fracture, and placing an appropriate sized plate on the fifth metatarsal, one would tap the hooks into the base of the metatarsal. The surgeon can use fluoroscopy to ensure proper alignment of the fracture and hook plate.

Proceed to insert a bone screw distal to the fracture, inserting it eccentrically to achieve a degree of compression. Then insert the remaining screws. Many times, it is possible to insert a long cancellous screw from a proximal position between the hooks of the plate across the fracture for greater stability if the avulsion fragment is large enough.

Other Pertinent Pearls

Surgeons may use intramedullary cancellous screws for both a Jones fracture and an avulsion fracture if the fragment is large. Use the largest diameter screw that will snugly fit in the medullary canal. If there is lateral bowing of the diaphysis, use a shorter screw that does not engage the diaphyseal curvature.

Diaphyseal fractures are almost always displaced and unstable. One can achieve stable fixation for most patients by using an inexpensive quarter tubular plate with 2.7 mm cortical bone screws. For patients with increased BMI or osteoporotic bone, the surgeon can use either a one-third tubular plate with 3.5 mm cortical bone screws or a locking plate.

In Summary

Although many different types of fixation have been advocated for fifth metatarsal fractures, we have reviewed the basic types of fixation that have given us the most consistent outcomes. Selection of fixation for a fracture is always the surgeon’s preference.

Dr. Fallat is the Program Director of the Podiatric Surgery Residency at the Oakwood Annapolis Hospital within the Oakwood Healthcare System in Wayne, Mich. He is a Fellow of the American College of Foot and Ankle Surgeons.

Dr. Chahal is a second-year podiatric surgery resident at the Oakwood Annapolis Hospital within the Oakwood Healthcare System in Wayne, Mich.

For further reading, see “Essential Insights On Treating Fifth Metatarsal Fractures” in the April 2006 issue of Podiatry Today, “Current Concepts In Treating Fifth Metatarsal Fractures” in the May 2010 issue or “Rethinking Our Approach To Jones Fractures To Facilitate Shorter Post-Op Recovery” in the December 2011 issue.